The present invention relates to a hand-held power tool, particularly a hand-operated angle grinder.
In particular it relates to such a hand-held power tool which has a device housing divided into a motor housing for receiving an electric drive, a gear head and a handle arranged on opposite ends of the housing and rotatable relative to the latter, and a positioning device for fixing housing parts in at least two different positions.
Presently, hand-held power tools, particularly hand-operated angle grinders, are outfitted with an on/off switch for the electric drive which is actuated via the switch strip. The switch strip is situated at the underside of the handle and is actuated by at least one finger when grasping the handle and held in an actuated position while working with the machine. The ergonomic design of the handle, e.g. the cross-sectional shape and angle of inclination relative to the device axis, is optimized for one individual working position of the machine.
Some hand-held power tools are used in more than one work position for various working operations. Apart from grinding or scouring, for example, an angle grinder is also used e.g. for parting or cutting stone slabs or plates. The optimal work position mentioned above is normally provided for the scouring work position in which the grinding disk faces downward, i.e. roughly parallel to the switch strip. However, for cutting work the angle grinder is rotated by 90.degree. toward the left or right around its longitudinal axis so that the cutting wheel is roughly vertical to the workpiece. Due to this rotation, the handle and switch strip assume an unfavorable position for the hand of the person grasping it. If the machine is rotated to the left and the handle is grasped with the right hand, the switch strip lies in the ball of the thumb. If the machine is rotated to the right and held in the right hand, the switch strip is only actuated and held by the thumb. In either case, it is not possible to hold the switch strip in a secure and comfortable manner. Moreover, in emergency situations the user cannot react quickly enough to switch off the machine in view of the position of the safety catch and switch lock.
To avoid this disadvantage there is already a hand-held power tool of the type mentioned above in which the handle part of the housing or the gear head part of the housing is held at the motor housing so as to be rotatable and can be fixed in defined rotational positions by a positioning device to achieve a working position which is more favorable ergonomically.
In a hand-held power tool of this type which has already been suggested (P 40 22 668.9) the rotation of the handle and gear head is enabled in that the shell-like housing of the rotatable housing part is provided with a radially projecting collar which engages in a circumferential groove at the motor housing. The manually actuated positioning device includes a locking arrangement for locking the rotatable housing part at the motor housing and a clamping device for clamping the rotatable housing part at the motor housing. The locking arrangement has at least two locking grooves which are arranged in the motor housing so as to be offset relative to one another by a rotational angle and a locking cam which can be swiveled in the shell housing of the rotatable housing part and is capable of positive engagement in one of the locking grooves. The clamping device has a clamping screw which extends transversely to a longitudinal slot in the projecting collar of the shell housing. The clamping screw can be screwed into a thread by a clamping lever and can cause the regions of the shell housing at both sides of the longitudinal slot to move together while reducing the width of the longitudinal slot. It is necessary to provide the clamping device in addition to the locking arrangement on the one hand so as to ensure a slight rotational movement of the rotatable housing part at the motor housing and on the other hand so that a rigid connection of the motor housing and rotatable housing parts is always provided when working with the hand-held power tool in different relative positions of these housing parts.